Observations

Description

Valves are lanceolate with wedge-shaped ends. The raphe is straight and filiform. The axial area is narrow and linear. The central area is round or transversely rectangular. Striae are radiate, becoming convergent at the valve apices. Striae number 11-13 in 10 µm. Areolae number approximately 30-33 in 10 µm. Striae are bent in the middle of the valve and short striae often alternate with longer ones around the central area.

Valve lanceolate with blunt, subrostrate ends. The central area is variable in shape, from circular to transversely rectangular. The raphe is straight, as are the proximal raphe ends.

Compare

The valves of N. recens differ from N. erifuga by the straight central raphe ends and generally wider valves. Navicula lanceolata has deflected central raphe ends, larger valves, and a larger central area. The valves of N. cari are more linear in shape. Navicula cari also has more radiate striae and denser areolae within each stria.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)

Autecology Discussion

This taxon prefers brackish water or fresh water of high mineral content, eutraphentic.

Habits

Size Range

101-1000 µm3 (ie Amphora veneta)

Motility

moderately motile (e.g. Navicula tripunctata)

Attachment

unattached

Habitat

benthic

Colony

EMAP Assessment

The Environmental Protection Agency (EPA) western Environmental Monitoring and Assessment Program (EMAP) study was completed during the years 2000-2004 (see citations at bottom of this page). Over 1200 streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming) were selected for sampling based on a stratified randomized design. This type of design insures that ecological resources are sampled in proportion to their actual geographical presence. Stratified randomized design also allows for estimates of stream length with a known confidence in several “condition classes” (good or least-disturbed, intermediately-disturbed, and poor or most-disturbed) for biotic condition, chemistry and habitat.

EMAP Distribution

Navicula recens

Distribution

The distribution map represents the relative abundance of this Navicula recens in the western EMAP study. Relative abundance is a measure of the proportion of cells of this species based on a "fixed count" of 300 total diatom cells counted and identified. Each of the western EMAP sample sites is shown, either with a black dot for sites where Navicula recens was not recorded, or with a red circle indicating the relative abundance of Navicula recens.

Note that the size of the proportional symbols varies between species to help show both abundant and rare species.

Scale for the map to the left

EMAP Response Plots

Navicula recens

Responses

The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Navicula recens from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)STRAHLER = distribution plot of the Strahler Stream Order SLOPE = stream reach gradient (degrees)W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.PHSTVL = pH measured in a sealed syringe sample (pH units)log_COND = log concentration of specific conductivity (µS/cm)log_PTL = log concentration of total phosphorus (µg/L)log_NO3 = log concentration of nitrate (µeq/L)log_DOC = log concentration of dissolved organic carbon (mg/L)log_SIO2 = log concentration of silicon (mg/L)log_NA = log concentration of sodium (µeq/L)log_HCO3 = log concentration of the bicarbonate ion (µeq/L)EMBED = percent of the stream substrate that is embedded by sand and fine sedimentlog_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.